Here is the picture of guitar. https://photos.app.goo.gl/kRjPwrUCL5ad5gT46 It is a hovner 185 guitar, how do I lower the action on this guitar?
Those guitars were never designed to have a low action - because they're acoustic, but were competing against big band instruments, the action was set high in order to make them louder. There was also a craze in the 1950's for Hawaiian sounds made with slides - again, that requires a high action.
The bridge on arch-top guitars are usually only held in position by string tension. If the thumbwheels are as far down as they can go, and the neck is straight and aligned correctly, you will need to have another bridge built for you.
This will give you a lower action, but you should definitely retain the old bridge in case you want to sell that guitar in future years.
Merely taking the bridge down lower may do it, using the adjusting screws under it. It may not.
The bridge should be the correct one for the guitar, in which case,if it's at its lowest point, and the strings are too high, the neck relief needs sorting. That's by using an Allen key in the end of the truss rod which is inside the neck. Usually accessed via the small plate on the guitar's headstock.
Be warned, it's not really a job for a beginner, as it's easy to wreck a guitar tightening up the trussrod.
If the actions only due to the high bridge, it's feasible to shave some off (not the saddle part !), so that there's adjustment to go lower. Again, if you don't know what you're doing, it's wrecking time.